The proposed study will (1) determine the prevalence of Alzheimer's disease (AD) in a rural population; (2) assess reliability and validity of a diagnostic screening protocol in predicting cases of probable AD without extensive diagnostic evaluation; (3) assess the reliability of each component test in the diagnostic screening protocol; (4) assess the validity of the Mini-Mental State Examination (MMSE) alone in predicting cases of probable AD; (5) test the hypothesis that a discriminant function derived from items of the MMSE and selected demographic characteristics (e.g. age, race) will better discriminate probable AD cases when used as screening instrument rather than the full MMSE; (6) identify other issues that may compromise the effectiveness of a diagnostic screening protocol among the rural elderly; (7) obtain baseline survey information regarding a sample of the elderly population of West Virginia (WV) as a basis for planning future strategies for case finding and management of AD statewide. Such baseline information will also be an invaluable resource for future studies of the longitudinal adverse and risk factors of AD and other dementing illnesses among the elderly. This is a two-stage, population-based study. The target population is all individuals 65 years and older residing in three West Virginia counties. A computer tape of Medicare beneficiaries will be used to identify eligible subjects. Lay interviewers will conduct stage 1 household diagnostic screening interviews, comprising various diagnostic components. All subjects screening positive for probable AD and a comparable number of subjects with negative screening results will participate in the stage 2 clinical evaluation, comprising physical examination, laboratory tests, and special diagnostic procedures for diagnosing probable AD according to NINCDS criteria and the preliminary findings of the principal investigator. Validity of the diagnostic screening protocol and its component tests will be assessed using criterion diagnoses determined by research physicians based on their review of results of the stage 2 clinical evaluation.